ABSTRACT

Genetic modification (GM) is the insertion, transfer or deletion of a gene or genes in an organism’s genome (its genetic material). It is typically visualized as the transfer of a gene/genes from one species to another by circumventing biological boundaries that prevent different species from exchanging their genetic material. In nature, the sharing of genetic material within eukaryotes (higher plants and animals) can take place only between members of the same species, or between closely related species. It should be noted that cross-species exchange can (and does) happen naturally. Bread wheat (Triticum aestivum), for example, is said to have originated in part from natural crosses between related grass species in the Fertile Crescent of the Middle East. The figure shown here is a highly simplified diagram of the origin of bread wheat. The shaded boxes and dashed lines indicate crossing with wild grasses (Aegilops species). As far as we can tell, there was no direct human intervention in the crosses, but it is likely that there was also a great deal of selection by farmers once crosses had occurred. The crosses involved the plants’ own mechanisms for sexual reproduction.